自定义循环显示暂停时"java.lang.UnsupportedOperationException"的过渡结果？

Question

我创建了一个自定义循环显示过渡，用作活动进入过渡的一部分(具体来说，我通过调用Window#setEnterTransition()将过渡设置为窗口的进入过渡(：

public class CircularRevealTransition extends Visibility {
    private final Rect mStartBounds = new Rect();
    /**
     * Use the view's location as the circular reveal's starting position.
     */
    public CircularRevealTransition(View v) {
        int[] loc = new int[2];
        v.getLocationInWindow(loc);
        mStartBounds.set(loc[0], loc[1], loc[0] + v.getWidth(), loc[1] + v.getHeight());
    }
    @Override
    public Animator onAppear(ViewGroup sceneRoot, final View v, TransitionValues startValues, TransitionValues endValues) {
        if (endValues == null) {
            return null;
        }
        int halfWidth = v.getWidth() / 2;
        int halfHeight = v.getHeight() / 2;
        float startX = mStartBounds.left + mStartBounds.width() / 2 - halfWidth;
        float startY = mStartBounds.top + mStartBounds.height() / 2 - halfHeight;
        float endX = v.getTranslationX();
        float endY = v.getTranslationY();
        v.setTranslationX(startX);
        v.setTranslationY(startY);
        // Create a circular reveal animator to play behind a shared
        // element during the Activity Transition.
        Animator revealAnimator = ViewAnimationUtils.createCircularReveal(v, halfWidth, halfHeight, 0f,
                FloatMath.sqrt(halfWidth * halfHeight + halfHeight * halfHeight));
        revealAnimator.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                // Set the view's visibility to VISIBLE to prevent the
                // reveal from "blinking" at the end of the animation.
                v.setVisibility(View.VISIBLE);
            }
        });
        // Translate the circular reveal into place as it animates.
        PropertyValuesHolder pvhX = PropertyValuesHolder.ofFloat("translationX", startX, endX);
        PropertyValuesHolder pvhY = PropertyValuesHolder.ofFloat("translationY", startY, endY);
        Animator translationAnimator = ObjectAnimator.ofPropertyValuesHolder(v, pvhX, pvhY);
        AnimatorSet anim = new AnimatorSet();
        anim.setInterpolator(getInterpolator());
        anim.playTogether(revealAnimator, translationAnimator);
        return anim;
    }
}

这正常工作正常。但是，当我在过渡过程中单击"后退按钮"时，出现以下异常：

Process: com.adp.activity.transitions, PID: 13800
java.lang.UnsupportedOperationException
        at android.view.RenderNodeAnimator.pause(RenderNodeAnimator.java:251)
        at android.animation.AnimatorSet.pause(AnimatorSet.java:472)
        at android.transition.Transition.pause(Transition.java:1671)
        at android.transition.TransitionSet.pause(TransitionSet.java:483)
        at android.app.ActivityTransitionState.startExitBackTransition(ActivityTransitionState.java:269)
        at android.app.Activity.finishAfterTransition(Activity.java:4672)
        at com.adp.activity.transitions.DetailsActivity.finishAfterTransition(DetailsActivity.java:167)
        at android.app.Activity.onBackPressed(Activity.java:2480)

我收到此错误有什么具体原因吗？应该如何避免？

Answer 1

您需要

创建一个忽略对pause()和resume()调用的Animator子类，以避免此异常。

有关更多详细信息，我刚刚在下面完成了有关此主题的帖子：

• 第 1 部分：http://halfthought.wordpress.com/2014/11/07/reveal-transition/
• 第 2 部分：https://halfthought.wordpress.com/2014/12/02/reveal-activity-transitions/

Answer 2

我收到此错误有什么具体原因吗？

ViewAnimationUtils.createCircularReveal是创建新RevealAnimator的快捷方式，是RenderNodeAnimator的子类。默认情况下，RenderNodeAnimator.pause抛出一个UnsupportedOperationException。您可以在堆栈跟踪中看到这种情况：

java.lang.UnsupportedOperationException
        at android.view.RenderNodeAnimator.pause(RenderNodeAnimator.java:251)

当棒棒糖中调用Activity.onBackPressed时，它会对Activity.finishAfterTransition进行新的调用，最终在Transition.pause(android.view.View)中回调Animator.pause，这是您的UnsupportedOperationException最终被抛出的时候。

转换完成后使用"后退"按钮时没有抛出它的原因是EnterTransitionCoordinator在完成后如何处理输入Transition。

应该如何避免？

我想你有几个选择，但都不是很理想：

选项 1

在调用Window.setEnterTransition时附加TransitionListener，以便监视何时调用"后退"按钮。所以，像这样：

public class YourActivity extends Activity {
    /** True if the current window transition is animating, false otherwise */
    private boolean mIsAnimating = true;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // Get the Window and enable Activity transitions
        final Window window = getWindow();
        window.requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);
        // Call through to super
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_child);
        // Set the window transition and attach our listener
        final Transition circularReveal = new CircularRevealTransition(yourView);
        window.setEnterTransition(circularReveal.addListener(new TransitionListenerAdapter() {
            @Override
            public void onTransitionEnd(Transition transition) {
                super.onTransitionEnd(transition);
                mIsAnimating = false;
            }
        }));
        // Restore the transition state if available
        if (savedInstanceState != null) {
            mIsAnimating = savedInstanceState.getBoolean("key");
        }
    }
    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        // Save the current transition state
        outState.putBoolean("key", mIsAnimating);
    }
    @Override
    public void onBackPressed() {
        if (!mIsAnimating) {
            super.onBackPressed();
        }
    }
}

选项 2

使用反射调用ActivityTransitionState.clear，这将阻止Transition.pause(android.view.View)在ActivityTransitionState.startExitBackTransition中被调用。

@Override
public void onBackPressed() {
    if (!mIsAnimating) {
        super.onBackPressed();
    } else {
        clearTransitionState();
        super.onBackPressed();
    }
}
private void clearTransitionState() {
    try {
        // Get the ActivityTransitionState Field
        final Field atsf = Activity.class.getDeclaredField("mActivityTransitionState");
        atsf.setAccessible(true);
        // Get the ActivityTransitionState
        final Object ats = atsf.get(this);
        // Invoke the ActivityTransitionState.clear Method
        final Method clear = ats.getClass().getDeclaredMethod("clear", (Class[]) null);
        clear.invoke(ats);
    } catch (final Exception ignored) {
        // Nothing to do
    }
}

显然，每个都有缺点。选项 1 基本上禁用"后退"按钮，直到过渡完成。选项 2 允许您使用"后退"按钮中断，但清除转换状态并使用反射。

这是结果的gfy。您可以看到它如何从"A"完全过渡到"M"并再次转换，然后"后退"按钮中断过渡并返回"A"。如果你看它，那会更有意义。

无论如何，我希望这对你有所帮助。

Answer 3

您可以添加侦听器以进入在方法onTransitionStart()/onTransitionEnd()中设置标志transitionInProgress的过渡。然后，您可以重写方法 finishAfterTransition() 然后检查transitionInProgress标志，并仅在转换完成后调用super。否则，您可以finish() Activity或不执行任何操作。

override fun finishAfterTransition() {
    if (!transitionInProgress){
        super.finishAfterTransition()
    } else {
        finish()
    }
}